In a variety of environments, including for example industrial environments, there is a need for control systems that are capable of governing the operation of one or more pieces of equipment or machinery in a manner that is highly reliable. Such control systems often employ a high degree of redundancy in their various circuits and other components, so as to guarantee or nearly guarantee that the control systems will achieve intended goals in operating the controlled equipment/machinery and, in the event of failures, that the control systems will operate in such manners that the control systems and the controlled equipment/machinery enter predicted failure states.
Among these control systems are control systems that are designed to disconnect, ground and otherwise isolate controlled equipment/machinery from one or more power sources in a predictable, reliable manner. Such control systems reduce the chance that the controlled equipment/machinery might be unintentionally restarted at times when it is being accessed by repair personnel or technicians for purposes of repair or modification, and thereby enhance the confidence and rapidity with which such personnel can accomplish such repairs/modifications. The power sources from which the controlled equipment/machinery are isolated by these control systems can include any of a number of power sources including, for example, electrical, pneumatic and hydraulic power sources.
Referring to FIG. 1, one Prior Art control system of this type is the ElectroGuard™ Bulletin 2030 Safety Isolation System available from Rockwell Automation, Inc. of Milwaukee, Wis., the beneficial assignee of the present application. This control system, shown in FIG. 1 as a control system 2, includes both an electric power isolation system 4 and a pneumatic (or hydraulic) power isolation system 6, and operates as follows.
When a failure or other condition occurs at a machine 8 of an industrial system 10 (in this case, an assembly line), and an operator appropriately switches or triggers a remote lockout switch (RLS) 12 associated with that machine to an “OFF” position, the control system 2 serves to disconnect both electric power and pneumatic power lines 15 and 16, respectively, from the machine so as to decouple the machine from both of those types of power. Additionally, the control system 2 then further serves to ground the machine 8.
Once the machine 8 has been isolated in this manner, an indication is provided to the operator (e.g., a light 18 turns on) indicating that it is appropriate for the operator to access the machine for purposes of making a repair or some other modification to the machine. Typically the operator will then access the machine by entering into a normally-inaccessible region, e.g., by opening a gate 20 and entering into the machine as shown (alternatively, for example, the operator could pass through a light curtain).
Once the operator has completed the repair/modification and left the normally-inaccessible region, the operator appropriately switches or triggers the RLS 12 again, this time to an “ON” position. After this occurs, the control system 2 reestablishes the connections between the power sources and the machine 8. The control system 2 typically employs redundant circuitry such as safety relays to enhance the control system's reliability in performing its control functions in this regard.
Although control systems such as the control system 2 shown in FIG. 1 are useful, such control systems are typically designed to have only limited purpose(s) and functionality. For example, the control system 2 merely serves the purposes of disconnecting/connecting one or more machines such as the machine 8 from electric and pneumatic power sources, grounding the machine(s), and conducting related communications with RLSs such as the RLS 12. In certain applications, however, it would be advantageous if such control systems could be reconfigured in a manner allowing for expanded functionality, particularly functionality involving control or monitoring of additional equipment/machines.
Despite the desirability of providing such additional functions in some circumstances, it is not possible to reconfigure conventional control systems such as the control system 2 to achieve such additional functions in the field. Largely this is because such conventional control systems are carefully designed to include sufficient redundancy to enhance reliability and behave in predictable manners during failures. Reconfiguration of such conventional control systems in the field could unpredictably alter the control systems' behavior and undermine the control systems' reliability, and consequently conventional control systems typically are designed in a manner that prevents such ad hoc reconfigurations.
Given that it would be desirable for reliable, failure-resistant control systems such as the control system 2 to have additional control and/or monitoring capabilities, and given that conventional systems of this type are not readily reconfigurable to provide such capabilities, it would be advantageous if an improved control system of this general type was developed that was capable of providing such capabilities. Further, it would also be advantageous if such an improved control system achieved similar levels of redundancy, reliability and failure-resistance as conventional control systems of this type.